This invention relates to self pressurized containers that are used for dispensing liquids or viscous materials. A container of this general type is described in a U.S. Pat. No. 4,387,833 issued to Frank Vanus, Jr. and it consists of an inner plastic liner to which is attached a dispensing valve. An elastic sleeve surrounds the inner plastic liner and it provides the dispensing pressure. The plastic liner and the elastic sleeve are contained in an outer shell for protection and for providing an outer surface that is usually decorated and printed. The outer shell has a bottom of such shape that the container will stand upright on a flat surface such as a shelf or table.
The container is filled at a factory by pressure flowing an agent thru the valve into and expanding the inner plastic liner and the elastic sleeve. The inner plastic liner is usually pleated to allow for the expansion. Because of the pleating of the inner plastic liner it is necessary that the bottom of the plastic liner have a semi-spherical, ovid or conical shape.
If the inner plastic liner is made of a strong material that has considerable dimensional stability when it is expanded, then the limit of the expansion will be delineated by the dimensions of the expanded plastic liner and the inner surface of the outer shell may not be touched in which case a conventionally designed outer shell having a flat or slightly recessed bottom as shown on the previously mentioned Venus Patent will be satisfactory and the outer shell as described in this invention will not be needed. However, strong plastic materials are usually expensive and also may not have the best barrier properties to be suitable for use in dispensing some kinds of agents
It may be desirable because of cost or other considerations to construct the inner plastic liner of weak materials such as polyethylene or other soft plastics in which case the expansion of the plastic liner when it is being filled must be limited by the inner surface of the outer shell rather than by the strength of the plastic liner, especially if excessive pressure is used in the filling process.
Most soft plastic materials have limited stretch or elongation properties and if pleated, a plastic liner would have to expand to fill the corners of a flat bottom outer shell, the materials in the plastic liner would either be ruptured or excessively thinned. It therefore becomes imperative that the bottom of the outer shell be shaped so as to minimize the amount of stretch or elongation of the plastic liner. This invention accomplishes that purpose.
An outer shell can be devised, that is made of two or more pieces to accomplish the purposes defined here, but it is quite evident that forming the bottom of the outer shell integrally as shown and described in the specification is the less costly process and will perhaps produce the higher quality product.